1. Field of the Invention
The present invention relates to a review apparatus for reviewing a specimen by moving a specimen stage to designated coordinates. In particular, the present invention relates to a defect review apparatus, as in a scanning electron microscope (SEM) defect review apparatus, for determining a review position by an automatic defect review (ADR) on the basis of information on a defect position detected by an inspection apparatus in an upper level.
The present invention also relates to a method and a review apparatus for setting a field of view for reviewing to have the optimum size by correcting designated coordinates and observation coordinates so that a specimen can be within the field of view for reviewing in order to achieve both high throughput and high accuracy of detecting a position of the specimen.
2. Description of the Related Art
In order to secure a high yield rate, for example, in a semiconductor fabrication process, it is important to find a defect, which occurs in the fabrication process, as early as possible to take appropriate measures against the defect as soon as possible. Nowadays, semiconductor devices are so miniaturized that even a minute defect may cause no longer negligible influence on the yield rate. For this reason, much smaller defects must be checked to avoid the yield rate decrease. An SEM defect review apparatus is one of important apparatuses for reviewing such a minute defect. In general, this kind of apparatus reviews a defect on the basis of the defect position detected in advance by an upper-level inspection apparatus such as an optical microscope and another SEM apparatus. When the defect is reviewed manually, a specimen stage is moved to the coordinates that are designated in an output from the upper-level inspection apparatus. Then, the specimen is imaged at a low magnification level at which the specimen can come within the field of view. After the defection position is visually checked, the stage is moved in a way that the defect position comes to the center of the field of view so as to acquire a defect image for reviewing at a high magnification. The apparatus having these steps automated is an automatic defect review (ADR).
The ADR performs image processing on a low magnification image for detecting a defect position (hereinafter, referred to as a “monitoring image”) to detect a defect appearing within the field of view of the monitoring image. A specimen stage is moved so that the detected defect can come to the center of the field of view. Subsequently, an image for reviewing (hereinafter, referred to as “review image”) is obtained at a high magnification that allows the defect to be detected easily in details. From the viewpoint of performing image processing, it is preferable to capture a monitoring image at a higher magnification to make the defect larger for reviewing. Nevertheless, if the magnification is too high, it is more likely that some defect would be outside the field of view (hereinafter, referred to as “view-field displacement”). For this reason, among the setting for the ADR, the setting of the magnification for the monitoring image is dependent on the experience of the user, and the magnification is a difficult parameter to set.
In particular, as a means for achieving both the detection of such a minute defect and the prevention of the view-field displacement together, there has been recently employed a method of enlarging the size of the field of view for reviewing without changing the magnification. However, this method requires the user to set the magnification for the monitoring image and the size of the field of view in combination, and thus produces a problem that it is even more difficult to set these parameters than otherwise.
As a method for effectively performing the magnification setting operation for the monitoring image, Japanese Patent Application Publication No. 2001-338601 (Patent Document 1) discloses a method in which a coordinate correcting expression is optimized so as to minimize the amounts of deviation between a defect position outputted from an upper-level inspection apparatus and an actually detected defect position. Moreover, Japanese Patent Application Publication No. 2002-131253 (Patent Document 2) discloses a method in which the magnification of the monitoring image is optimized on the basis of detected deviation amounts.